The scrubber in Problem 21. 23 has been running well for several years. It is now observed that the outlet solute mole fraction in air is 0. 002 . Suggest at least five reasons for this observation. Suggest at least five ways to compensate for this problem in the short term. Evaluate each compensation method as to its suitability.

Data from problem 21.23

 A packed scrubber with 20 transfer units has been designed to reduce the solute concentration in \(80 \mathrm{kmol} / \mathrm{h}\) of air from a mole fraction of 0.01 to 0.006 . The solute is absorbed into a \(20 \mathrm{kmol} / \mathrm{h}\) solvent stream, and it can be assumed that the solvent stream enters solute free. If the flow of solvent is decreased by \(15 \%\), what is the new outlet mole fraction of solute in air?